3. Taming the screw

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It is often assumed that two opposing ideas can never come together to solve problems. That is a wrong assumption. And this is best demonstrated in an invention called the turnbuckle.

We all know about the screw and how it is nothing but an inclined ramp wound around a cylinder. And we know how a ramp makes it easy to push something up away from the pull of gravity. The act of screwing is moving the tip of the screw (which is also a simple machine — a wedge) into the object being screwed, via the spiral ramp. The tip of the screw, and the sharpe edges of the spiral ramp gets wedged into the body of the object and establishes a firm grip.

It is the act of unscrewing which is interesting: We all know that if we reverse the rotation of the tightened screw, it will come loose. This can also happen if there are some forces which will generate the reversed rotation. (i.e. one need not actually take a screwdriver and unscrew the screw). Such a situation can be demonstrated by a simple exercise.

Imagine a tug-o-war game, where the cable is actually cut in the center into two pieces and those two pieces are re-joined at the center using a screw and a nut, between the two opposing parties. i.e. One end of one part is a screw, which is screwed onto a nut which is welded to the end of the other part. Now when the game is on, and both the parties are pulling on the cable; and if the tension force applied on the cable is perfectly axial then the screw would hold tight. However, if there are some sideways force (torque) on the screw then it can result in an unscrewing motion. Eventually, the screw would get dislodged from the nut and the cable would come apart at the center.

It is for this reason, a simple screw and a nut arrangement can never be used for holding a cable tight. We need to use a turnbuckle for that. For example, in a sailboat, the sail needs to be kept uniformly taut and to do that the cables (called shrouds and forestays) from the central mast needs to be kept at a constant tension irrespective of the various movements of the boat. The cable is tightened by using a turnbuckle at its end. A turnbuckle has a pair of screws and nuts as seen in the figure. The nuts are actually integrated into one physical link which establishes the continuity of the cable. One can tighten or loosen the turnbuckle by rotating the link of the turnbuckle.


The threading of these two screws of a turnbuckle are in opposite directions of each other. So a loosening force applied at one end of the turnbuckle will result in the tightening action at the other end. Similarly, the other way around: If there is a tightening torque at one end, it would loosen the screw at the other end. Therefore, once the link of the turnbuckle is tightened to generate a particular tension in the cable, rotational forces that the cable is naturally subjected due to the movement of the boat would not result in the tension changing ever. The cable would remain tensioned to the same level throughout. If the cable fails, it would always be because of metalurgical failure.

A turnbuckle is a fascinating example which demonstrates that two opposite forces can come together to achieve a single purpose. Without a turnbuckle, one would never have a sailboat or the electric transmission wires, or … in fact … almost anything which involves a cable.

The turnbuckle has important lessons for an architect. I remember this particular design assignment clearly: I had to fit in a dining table in one corner of the room. That was the only corner available. The problem was that there was a column right there and try as we may, there was no way we could have fitted a regular dining table there. Invariably, the column intruded. We spent quite some time cursing the column — and the builder and the earlier architect who had designed that apartment and anyone else who came in close range. My client was quite vexxed too: his time schedules were all getting upset, and here we were; still not sure how to go about with the blessed dining table.

One day I went to the site when nobody was around and took a hard look at that corner. It seemed to me that the column was staring back at me quite blankly. Initially I was perplexed, then I started laughing. I said I am going nuts: How on earth can I personify the column? The column exists. And there is nothing more to it. I now need to know how to get somebody to eat in that blessed corner. Let us start with the basics… Wait a sec! That is when it struck me : What I need is not a dining table there, but to promote the activity of dining. So I said that instead of fighting the presence of the column, why not integrate that into the activity?. Once that mental block was broken through, the rest was easy. Shortly later, I could flesh out the design of a dining table top which didnt have any base. It was simply cantilevered out from the column! When it was all ready and done, those who saw it, did not even realize that there was a problem there to begin with.

I believe good design solutions should ideally have such a characterestic: It should solve problems in such a manner that people should not even detect that there was a problem that was needed to be addressed in the first place. I believe that much of good design in India does display such a characterestic: They do not shout from the roof top about what they had solved. They are just there. Good designs remind me of water: It is remarkable that water is tasteless; it is neither alkaline or acidic (i.e. it does not "shout") and yet it is still so important for life. I believe good designs sits between two equally and opposite forces, like the turnbuckle.

As a side note: it is difficult to prove whether India does have good architecture or not. Because sometimes there is no way to be sure whether the architect drove away the problem completely (as in the above example) or whether the architect only ended up doing something mediocre which never had to solve any problem in the first place. I guess some kind of "before" and "after" documentation (like the ones you see in slimming advertisements ) would help in establishing the truth, but for want of that we cant be sure. I am sure there are other sides to this story which are best explored elsewhere.

In conclusion, one way of solving problems is to fully understand how two ideas that are opposed to each other can actually join up to create a strong whole. In the case of the dining table, whenever I thought the column was opposed to the dining table, I could not think of a solution — but the moment I realized that the dining table can be cantilevered off the column then presto, everything fitted in.


  1. http://www.tridenttech.org/atemmg/SCREW/Screw.htm
  2. http://www2.milwaukee.k12.wi.us/science/pdf/4Science/4thSimpMachnReaddoc.pdf

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